Device for positioning and securing a part having circular regions

Abstract

A device comprises two jaws arranged to be pressed one against the other and to grasp a part to be positioned and secured. The part and/or the jaws comprise circular regions presenting a succession of planar or curved facets regularly disposed over said regions, with adjacent facets forming obtuse angles between them whose vertices define sharp edges or points. In a preferred embodiment, the jaws clamping a part having a rounded portion are tightened by means of two screws whose centerlines form an angle with each other, so that upon tightening of the jaws, at least one of the jaws flexes so as to assure a better grip of the rounded portion of the part.

I claim: 
     
       1. A system comprising a part to be positioned and secured and a device for positioning and securing said part, said device comprising two jaws arranged to be pressed against each other to clamp said part, wherein at least one element selected from the group consisting of said part and said jaws comprises at least one region, the cross-section of which is circular, wherein said at least one region has a succession of facets with polygonally-shaped boundaries regularly arrayed over at least a portion of said at least one region, wherein adjacent facets meet at obtuse angles and wherein the boundaries between adjacent facets are sharp edges and sharp points. 
     
     
       2. A system of claim 1 wherein said at least one region is located on said part to be positioned and secured and wherein the surfaces of the jaws in contact with said part are smooth. 
     
     
       3. A system of claim 2 wherein the part to be positioned and secured comprises a sphere having at least one faceted segment. 
     
     
       4. A system of claim 1 wherein said part has the form of a cylinder having at least one faceted region. 
     
     
       5. A system of claim 2 wherein said at least one faceted region has the shape of a truncated cone. 
     
     
       6. A system of claim 4 wherein the cylinder includes a central bore parallel to the axis of said cylinder. 
     
     
       7. A system of claim 1 wherein said succession of facets is disposed on a material harder than the material gripping said faceted regions. 
     
     
       8. A device for positioning and securing at least one part having a rounded portion, said device comprising members adapted to be disposed facing one another and to firmly clamp said part between them, with said members being capable of being pressed together by at least two screws whose centerlines form an angle with each other, so that upon tightening of said screws at least one of said members flexes so as to more firmly secure the rounded portion of said part and including also in combination therewith a part to be positioned and secured and including a rounded portion which is a sleeve comprised of a portion defining a spherical envelope. 
     
     
       9. A device of claim 8 wherein said portion defining a spherical envelope has a central passage. 
     
     
       10. A device of claim 8 wherein the material of the sleeve has a greater hardness than that of the members surrounding it. 
     
     
       11. A device of claim 9 wherein said spherical portion is extended by at least one tubular portion enclosing said central passage. 
     
     
       12. A device of claim 9 wherein said sleeve comprises a spherical portion constituted by two shells, each shell with a lateral trough forming half of a central passage passing through said spherical envelope. 
     
     
       13. A device of claim 9 wherein said central passage is of polygonal cross section. 
     
     
       14. A device of claim 9 wherein said central passage is of elliptical cross section. 
     
     
       15. A device of claim 9 wherein said central passage is adapted to accommodate a frame bar of an external bone fixation appliance.